FIG. 1 depicts a conventional method 10 for forming a tunneling magnetoresistive element in a read transducer. The read transducer includes a magnetic tunneling junction formed using the method 10. The layers in the magnetoresistive sensor, or stack, below the conventional tunneling barrier layer are deposited, via step 12. The magnetoresistive stack is typically formed on other structures, such as, shield(s), and/or write transducer(s). The magnetoresistive stack layers are typically blanket deposited. The layers below the tunneling barrier layer typically include seed layer(s), a conventional antiferromagnetic (AFM) layer, and a conventional pinned layer. A metallic Mg layer may optionally be deposited, via step 14. The Mg layer may be desired for the conventional MgO barrier layer. A conventional MgO barrier layer is deposited, via step 16. The conventional MgO barrier layer is a crystalline insulator. After deposition of the conventional MgO barrier layer, the transducer may be heated at a high temperature in situ, via step 18. Thus, the conventional transducer may be heated in the deposition chamber in which the MgO barrier layer is formed. In general, a high temperature on the order of three or four hundred degrees Celsius or higher is used. A free layer is provided, via step 20. Fabrication of the conventional tunneling magnetoresistive element, as well as the remainder of the transducer may then be completed, via step 22. Step 22 may include defining the conventional tunneling magnetoresistive element, which is to be a read sensor, in the track width and stripe height directions. Other structures, such as hard bias structures, contacts, shields, and write transducers may also be formed. The track width direction is parallel to the air-bearing surface (ABS) and generally perpendicular to the layers of the magnetoresistive stack.
Although the method 10 may be used to fabricate a tunneling magnetoresistive element, there may be drawbacks. For use in high density magnetic recording devices, for example on the order of five hundred gigabits per square inch it is desirable for the tunneling magnetoresistive element to have certain characteristics. A low resistance times area (RA), for example less than one Ω-μm2, as well as a high tunneling magnetoresistance (TMR) are desired for fast recording and a high signal to noise ratio (SNR). However, the conventional crystalline tunneling barrier fabricated using the conventional method 10 may produce insufficient RA and TMR for high density recording applications. Use of the Mg layer provided in step 14 may improve the crystallinity of the conventional MgO barrier layer and thus the RA and TMR. However, the improvement in RA and TMR may be insufficient. Further, heating performed in step 18 may not significantly improve the conventional MgO barrier layer and may cause diffusion of portions of the pinning layer and SAF, which adversely impacts performance of the conventional magnetic element. Consequently, an improved tunneling barrier layer and thus an improved magnetoresistive element for use in high density recording are still desired.